1. Hair as Evidence Resists chemical decomposition. Retains its structural features over long periods of time. Humans lose about 100 hairs per day so they transfer often and can link suspect, victim and crime scene. An individual hair cannot result in definitive identification of a person unless it has a DNA tag attached.

2. The Function of Hair Regulate body temperature Decrease friction Protect against sunlight Increase sense of touch

3. The Structure of Hair The hair shaft -is composed primarily of keratin, a protein which makes hair resistant to physical change. Each strand grows out of a follicle which is a club shaped structure in the skin. Papilla is a network of blood vessels at the end of the follicle that supply nutrients to help the hair grow. The sebaceous gland secrets oil that helps keep the hair conditioned.

4. The Structure of Hair The hair shaft is made up of 3 main parts. Structure of a hair: –Cuticle: outer layer of scales of hardened, flattened, keratinized tissue which overlap each other and point from proximal to distal (close to root –farthest from root) –Cortex: largest part of the shaft which contains the pigment granules (melanin) that gives hair its color. –Medulla: hollow tube or rows of dark-colored cells organized in a pattern specific to the animal species –Cortical fusi: air spaces

5. Cuticle Structures Coronal Spinous Imbricate *human

6. Medulla Patterns There are 5 medulla patterns shown above

7. Medullary Index Medullary Index (medulla/shaft diameter) human hair generally <1/3 animal hair >=1/2 Animal hair and human hair have several differences, including the pattern of pigmentation, medullary index, and the cuticle type. Pigmentation in human hair tends to be denser toward the cuticle, in animals it is denser toward the medulla. Animal pigments are often found in solid mases called ovoid bodies. Human hairs are usually one color while animal hairs can change color abruptly in a banded pattern.

8. Is It Animal or Human? (A) (B) (C) (D)

9. Types of Hair Hair can vary in shape, length, diameter, texture, and color. Cross-sections of hair can be circular, triangular, irregular, or flattened, influencing the curl of the hair Texture of hair can be coarse or fine Forensic scientists distinguish six types of hair on the human body: 1. Head hair – circular or elliptical 2. Eyebrows and eyelashes – circular/tapered 3. Beard and mustache – thick, triangular, course, double medulla 4. Underarm- oval or triangular 5. Auxiliary or body – oval or triangular, blunt or frayed end 6. Pubic – oval or rectangular, buckling

10. Hair Growth Hair growth stages (Remember ACT): –Anagenic: hair follicle is actively producing the hair; follicle is attached to root (10-1000 days) 80-90% of all human hair is this active growth stage. –Catagenic: transition stage in which the root is pushed out of the follicle (14-21 days) 2% of all hair growth and development. Hair grows and changes, perhaps turning gray. –Telogenic: hair naturally becomes loose and falls out,10-18% of hair are in this stage.

11. Treated Hair Bleaching hair removes pigment granules and gives hair a yellowish color, it also makes hair brittle and can disturb the scales on the cuticle. Dying hair changes the color of the hair shaft, and the cuticle and cortex both take on the color

12. Racial Differences Asian European African

13. Human Hair As Class Evidence Can sometimes determine racial origin

14. Human Hair As Class Evidence or Individual Evidence Can often determine body area of origin Can determine shed or cut vs. forcibly removed Forcibly removed hair like that on the left can become individual evidence because nuclear DNA can be recovered and analyzed. DNA could be found from tissue present No DNA likely Testing the Hair Follicle If hair is forcibly removed the entire hair follicle may be present. This is called a follicular tag. Blood and tissue attached to the follicle may be analyzed for blood proteins, blood type, or DNA analyses.

15. Collect hair and fiber evidence by using –Wide, transparent sticky tape –Lint roller –Evidence vacuum cleaner If fibers must be removed from an object –Use clean forceps –fold fiber into a small sheet of paper –store in paper bag Collecting Hair and Fiber Evidence

16. Collection of Hair Evidence Questioned hairs must be accompanied compared with an adequate number of control samples –from victim –from suspects –From animals Representative control samples –50 full-length hairs from all areas of scalp –25 full-length pubic hairs

17. Forensic Analysis of Hair The following questions apply to hair evidence: –Is the hair human or animal? –Does it match the hair of the suspect? –Does it have a follicle for DNA testing? Cat Human

18. Macro & Microscopic Forensic Analysis Hair is studied macroscopically and microscopically. –Macroscopic – length, diameter, color, curliness –Microscopic Microscopic – pattern of the medulla, pigmentation of the cortex, types of scales on the cuticle, area of origin, dye if applicable Comparison Microscope is used to find “consistencies” between suspect and crime scene hair. Phase contrast microscope- Uses filters to show more hair features. Fluorescent microscope - uses light that causes certain chemicals to glow if present. Comparison Microscope

19. Chemical Testing Chemical- testing for substances in the hair shaft. Because hair grows out of the skin, chemicals that the skin absorbs can become incorporated into hair. Hair is dissolved in an organic solvent that breaks down the keratin and releases any substances that have been incorporated into the hair. Hair grows about 1.3cm/month. Looking at the length of hair containing chemicals tells how long they were being ingested. Example 6.5 cm of hair with drug, shows 6 months of use.

20. Nuclear Activation Analysis Neutron activation analysis (NAA) – can identify up to 14 different elements in a single 2 cm long strand of hair. The hair is placed in a nuclear reactor and bombarded with high-energy neutrons. Different elements will give off gamma radiation with different signals that can be recorded. The probability of 2 individuals having the same concentration of nine different elements is about one in a million.